Heat blocks and heating

ABSTRACT

An apparatus and method for a thermal system comprising a top plate having a non-metal material wherein the top plate comprises a plurality of heating wells, each heating well sized to accommodate a plurality of sample tubes containing samples. A bottom plate engages to the top plate to form a heat block. A plurality of heat transfer pins extend from the bottom plate to the top plate. The non-metal material of the top plate may be molded to engage the heat transfer pins and increase heating efficiency. The invention also includes a heat block that includes a thermal plate comprising a thermally conductive material, the thermal plate including a major upper surface having a substantially planar area and a plurality of heating wells for accepting a plurality of sample tubes; and a heating plate engaging the thermal plate and contacting the major upper surface of the thermal plate. The heat block may be used for efficient thermal cycling of biological samples.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application Ser. No. 60/691,124, filed on Jun. 16, 2005, which is hereby incorporated by reference in its entirety.

FIELD

The embodiments disclosed herein relate to heating samples of biological material, and more particularly heating and thermal cycling of DNA samples to accomplish a polymerase chain reaction, a quantitative polymerase chain reaction, a reverse transcription-polymerase chain reaction, an immuno-polymerase chain reaction, or other nucleic acid amplification types of experiments.

BACKGROUND

Techniques for thermal cycling of DNA samples are known in the art. By performing a polymerase chain reaction, DNA can be amplified. It is desirable to cycle a specially constituted liquid biological reaction mixture through a specific duration and range of temperatures in order to successfully amplify the DNA in the liquid reaction mixture. Thermal cycling is the process of melting DNA, annealing short primers to the resulting single strands, and extending those primers to make new copies of double stranded DNA. The liquid reaction mixture is repeatedly put through this process of melting at high temperatures and annealing and extending at lower temperatures.

In a typical thermal cycler, a biological reaction mixture including DNA will be provided in a large number of sample wells on a thermal block assembly. It is desirable that the samples of DNA have temperatures throughout the thermal cycling process that are as uniform as reasonably possible. Even small variations in the temperature between one sample well and another sample well can cause a failure or undesirable outcome of the experiment. For instance, in quantitative PCR, one objective is to perform PCR amplification as precisely as possible by increasing the amount of DNA that generally doubles on every cycle; otherwise there can be an undesirable degree of disparity between the amount of resultant mixtures in the sample wells. If sufficiently uniform temperatures are not obtained by the sample wells, the desired doubling at each cycle may not occur. Although the theoretical doubling of DNA rarely occurs in practice, it is desired that the amplification occurs as efficiently as possible.

In addition, temperature errors can cause the reactions to improperly occur. For example, if the samples are not controlled to have the proper annealing temperatures, certain forms of DNA may not extend properly. This can result in the primers in the mixture annealing to the wrong DNA or not annealing at all. Moreover, by ensuring that all samples are uniformly heated, the dwell times at any temperature can be shortened, thereby speeding up the total PCR cycle time. By shortening this dwell time at certain temperatures, the lifetime and amplification efficiency of the enzyme are increased. Therefore, undesirable temperature errors and variations between the sample well temperatures should be decreased.

Prior art heat blocks composed of all metal can be expensive. In metal machined blocks or metal, thick base, electro-formed blocks, the primary heat transfer path, from the heating means to the well cavity, is limited by the wall area of the well. That is, the heat must move from the bottom of the block through the wall area of the well to heat the well cavity. To promote heat distribution the well wall is made as thin as possible to maximize the heating ramp rate of the well cavity.

In light of the foregoing, there is a need for a thermal cycling apparatus and method that enhances temperature uniformity of the sample wells to improve the efficiency or accuracy of processing samples. Thus, there is a need in the art for an apparatus and method for a non-metal block thermal system for thermal cycling a plurality of samples.

SUMMARY

In accordance with one aspect of the invention, an apparatus and method are provided for a non-metal block thermal system comprising a top plate having a non-metal material wherein the top plate comprises a plurality of heating wells, each heating well sized to accommodate a plurality of sample tubes containing samples. A bottom plate engages to the top plate to form a heat block. A plurality of heat transfer pins extend from the bottom plate to the top plate. The plurality of heat transfer pins deliver heat to the plurality of heating wells. The non-metal material of the top plate may be molded to engage the heat transfer pins and increase heating efficiency. The heat block may be used for efficient thermal cycling of biological samples.

One heat block in accordance with this aspect of the invention comprises a top plate comprising a non-metal material wherein the top plate comprises a plurality of heating wells for accepting a plurality of sample tubes; a bottom plate engaging the top plate; and a plurality of heat transfer pins extending from the bottom plate to the top plate to transfer heat from the bottom plate to the top plate.

One heat block in accordance with this aspect of the invention comprises a top plate comprising a non-metal core with a metal coating on an outer surface and a bottom plate comprising a metal.

The present invention also provides a method of thermal cycling samples comprises placing a plurality of sample tubes containing samples in a sample retainer, rotating a rotating heat assembly to position a top plate of a heat block below the sample retainer, the top plate comprising a plurality of heating wells; raising the rotating heat assembly to bring the plurality of heating wells of the top plate in thermal contact with the plurality of sample tubes; heating the heat block to a first temperature for a first time period to control a temperature of the samples in the plurality of sample tubes; and lowering the rotating heat assembly so the plurality of heating wells of the top plate are no longer in thermal contact with the plurality of sample tubes.

The present invention further provides a method for heating a plurality of heating wells comprises providing a heat block having a top plate comprising a non-metal material and a bottom plate with a plurality of heat transfer pins engaging a plurality of heating wells of the top plate; placing the plurality of heating wells in thermal contact with a plurality of sample tubes; heating the bottom plate of the heat block with a heater; and transferring heat from the bottom plate to the plurality of heating wells by the plurality of heat transfer pins.

In accordance with a second aspect of the invention, one or more thermally conductive materials are used to form at least one plate of a heat block. One heat block in accordance with this aspect comprises a thermal plate comprising a thermally conductive material, the thermal plate including a major upper surface having a substantially planar area and a plurality of heating wells for accepting a plurality of sample tubes; and a heating plate engaging the thermal plate and contacting the major upper surface of the thermal plate.

The thermally conductive material can be aluminum.

Additionally, the thermal plate can include a boss having a cavity defined therein to simulate a temperature response of a biological sample. Alternatively, or in addition, one heating well of the heat block can be used to measure a simulated biological fluid sample temperature.

One heat block in accordance with this second aspect includes a first plate having a substantially planar major upper surface and a plurality of heating wells defined in the major upper surface for accepting a plurality of sample tubes; and a second plate abutting the major upper surface of the first plate, the second plate being a heating plate having a body portion having a plurality of apertures formed therein, where the body portion can be substantially planar in shape; an insulative portion surrounding the plurality of apertures; and a heating element carried by the heating plate, arranged between insulative portions thereof.

The heating element can be a resistive heating element, or a tubular conduit for carrying heated fluid, and can be secured to a bottom surface of the second plate, for contacting the first plate, embedded in the second plate, or formed within in the second plate.

The insulative portion can be thermally insulative, or electrically insulative.

The heat block can also include connecting portions for connecting the heating element of the second plate to a heat energy source. The heat energy source can be an electrical energy source for providing an electrical current to the heating element, or can be an energy source that provides heated fluid to the heating element.

Preferably, the first plate comprises a metal material, and can include copper, aluminum, brass and combinations thereof. The metal material of the heat block can also include a first metal coated with a second metal.

The present invention also provides a method for heating a plurality of heating wells comprising; providing a heat block having a thermal plate comprising a thermally conductive material, the thermal plate including a major upper surface having a substantially planar area and a plurality of heating wells for accepting a plurality of sample tubes; and a heating plate engaging the thermal plate and contacting the major upper surface of the thermal plate; placing the plurality of heating wells in thermal contact with a plurality of sample tubes; heating the thermal plate of the heat block with the heating plate; and transferring heat from the thermal plate to the plurality of heating wells through conductive heat transfer.

In one embodiment, the thermal plate of the heat block is heated prior to the step of placing the plurality of heating wells in thermal contact with the plurality of sample tubes.

The present invention also provides a method of thermal cycling samples comprises placing a plurality of sample tubes containing samples in a sample retainer, rotating a rotating heat assembly to position a top plate of a heat block below the sample retainer, the top plate comprising a plurality of heating wells; raising the rotating heat assembly to bring the plurality of heating wells of the top plate in thermal contact with the plurality of sample tubes; heating the heat block to a first temperature for a first time period to control a temperature of the samples in the plurality of sample tubes; and lowering the rotating heat assembly so the plurality of heating wells of the top plate are no longer in thermal contact with the plurality of sample tubes, and wherein the heat block comprises a first plate having a substantially planar major upper surface and a plurality of heating wells defined in the major upper surface for accepting a plurality of sample tubes; and a second plate abutting the major upper surface of the first plate, the second plate being a heating plate having a body portion having a plurality of apertures formed therein; an insulative portion surrounding the plurality of apertures; and a heating element carried by the heating plate, arranged between insulative portions thereof.

The heat block improves heat transfer, efficiently processes samples, and allows for substantial cost savings through the use of a top plate comprising a non-metal material.

BRIEF DESCRIPTION OF THE DRAWINGS

The presently disclosed embodiments will be further explained with reference to the attached drawings, wherein like structures are referred to by like numerals throughout the several views. The drawings are not necessarily to scale, the emphasis having instead been generally placed upon illustrating the principles of the presently disclosed embodiments.

FIG. 1 shows an assembly view of a heat block wherein a top plate of the heat block is disengaged from a bottom plate of the heat block.

FIG. 2 shows a perspective view of a bottom plate of a heat block.

FIG. 3 shows a top perspective view of a top plate of a heat block.

FIG. 4 shows a bottom perspective view of a top plate of a heat block.

FIG. 5 shows a cut away view of a heat block wherein a top plate is engaged to a bottom plate.

FIG. 6 shows an alternative embodiment of the heat block.

FIG. 7 shows a view of a block heater of a heat block.

FIG. 8 shows a perspective view of a central tube of an embodiment wherein multiple heat blocks may engage the central tube.

FIG. 9 shows a perspective view of a rotating heat assembly wherein a plurality of heat blocks engage the central tube.

FIG. 10 is a top perspective view of a thermal plate in accordance with the invention.

FIG. 11 is a bottom perspective view of the thermal plate of FIG. 10.

FIG. 12 is a bottom perspective view of a heating plate in accordance with the invention.

FIG. 13 is top perspective view of a heat block assembly in accordance with the invention, illustrating the thermal plate of FIGS. 10 and 11 and the heating plate of FIG. 12 in an abutting configuration.

FIG. 14 is a perspective view of a rotating heat assembly including three heat block assemblies as shown in FIG. 13.

FIG. 15 shows a perspective view of a rotating heat assembly as part of a processing apparatus.

FIG. 16 shows a close up view of a rotating heat assembly as part of a processing apparatus.

FIG. 17 shows a perspective view of a rotating heat assembly as part of a processing apparatus.

While the above-identified drawings set forth presently disclosed embodiments, other embodiments are also contemplated, as noted in the discussion. This disclosure presents illustrative embodiments by way of representation and not limitation. Numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of the presently disclosed embodiments.

DETAILED DESCRIPTION

A heat block is capable of delivering a desired amount of heat uniformly and efficiently to a plurality of samples. The heat block comprises a metal and/or a non-metal material to increase the efficiency of processing samples while reducing the cost of constructing the heat block.

Thermal cyclers are the programmable heating blocks that control and maintain the temperature of the sample through the three temperature-dependent stages that constitute a single cycle of PCR: template denaturation; primer annealing; and primer extension. These temperatures are cycled up to forty times or more to obtain amplification of the DNA target. Thermal cyclers use different technologies to effect temperature change including, but not limited to, peltier heating and cooling, resistance heating, and passive air or water heating.

Thermal cycling of DNA can accomplish a polymerase chain reaction (PCR), a quantitative polymerase chain reaction (qPCR), a reverse transcription-polymerase chain reaction (RT-PCR), a reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immuno-polymerase chain reaction (I-PCR), or other nucleic acid amplification types of experiments.

A heat block is shown generally at 67 in FIG. 1. The heat block 67 comprises a top plate 83 and a bottom plate 75. In this embodiment, the top plate 83 comprises a non-metal material. The top plate 83 may be composed of any plastic material which may be molded and has physical properties sufficient to satisfy the structural and temperature requirements. The top plate 83 comprises a high-temperature moldable plastic. The top plate 83 may comprise polyphenylene sulfide (PPS), polyetherimide (PEI) or other similar materials known to those skilled in the art.

In certain embodiments, the top plate 83 comprises a metal coating over a non-metal material. The metal coating is on an outer surface of the top plate 83. The metal coating acts as a wear surface and permits easy cleaning of the top plate 83. The metal coating also promotes the sensitivity of the instrument, when used to obtain quantitative data, by providing a more optically reflective surface as compared to the molded plastic surface. The metal coating or plating may comprise copper, nickel, chromium, gold, or a combination of multiple metals or other metals known to those skilled in the art. The metal coating may be applied using coating methods known in the art including, but not limited to, bath plating, physical, chemical, or ion vapor deposition, or other coating methods known in the art.

The bottom plate 75 comprises a conductive material, preferably a metal. The bottom plate 75 may be prepared by casting, machining, forging, metal injection molding or other methods known in the art. In an embodiment, the bottom plate 75 comprises aluminum. The bottom plate 75 may comprise copper, silver, aluminum alloy, other castable alloys or other similar materials known to those skilled in the art. The bottom plate 75 may comprise a plurality of metals. Those skilled in the art will recognize that the bottom plate may comprise a variety of conductive materials and be within the spirit and scope of the presently disclosed embodiments.

The design of the top plate 83 in relation to the bottom plate 75 allows for heat to be more evenly distributed throughout a sample which leads to more uniform, efficient and reliable results as compared to those obtained through the use of prior art heat blocks. The use of a non-metal material for the top plate 83 is cost effective. Processing a large number of samples often requires the use of a large number of heat blocks which increases expenses. The presently disclosed embodiments allow for substantial cost savings by using heat blocks that can have a non-metal top plate. As such, the presently disclosed embodiments provide both cost savings and improved results.

FIG. 1 shows an assembly view of a heat block wherein the top plate 83 of the heat block 67 is disengaged from the bottom plate 75 of the heat block 67. A plurality of heat transfer pins 77 extend from the bottom plate 75. The plurality of heat transfer pins 77 may be formed with the bottom plate 75. Alternatively, the plurality of heat transfer pins 77 may be added to the separate bottom plate 75. The plurality of heat transfer pins 77 may be composed from a different material than the bottom plate 75. The plurality of heat transfer pins 77 may be different shapes including, but not limited to, square, rectangular, circular, oval, and other shapes. The plurality of heat transfer pins 77 may be etched, roughened, grooved, notched or formed with any other surface effect such that the surface area for each pin is increased. This may be useful to promote a mechanical connection with a plurality of ribs 87 of the top plate 83.

The plurality of heat transfer pins 77 deliver heat to a plurality of heating wells 85. The plurality of heat transfer pins 77 distribute heat evenly to each individual sample. The plurality of heat transfer pins 77 transfer heat to the sides of the plurality of heating wells 85 that contain the plurality of sample tubes 39. The plurality of heat transfer pins 77 act as an interface to deliver heat along the entire length of the sample tube 39. Delivering heat to the sides of the heating well 85 distributes heat in a sample better than delivering heat to the sample exclusively through the bottom of the heating well 85. The heating well 85 is molded so that the heating well 85 better engages the heat transfer pins 77 and therefore allows for heat to be efficiently delivered to the heating well 85 from the sides of the heating well 85 through thermal conduction. The flexibility and moldability of the non-metal material of the top plate 83 to engage the heat transfer pins 77 provides uniform heating to the sample and increases processing efficiency. The heating well 85 may have the plurality of ribs 87 to engage the plurality of heat transfer pins 77 and promote uniform heat distribution.

The heating ramp rate is important as a user feature since it impacts the speed at which a user can conduct a biological experiment. As the heating well wall thickness is reduced, to reduce the amount of heated mass, the area for the heat path is reduced as well. As the heating well wall thickness is reduced, the temperature gradient within a single heating well cavity increases. This single well temperature gradient may become as great or greater than the temperature gradient across the entire sample block for thin well walls. The plurality of heat transfer pins 77 combined with the top plate 83 allows the heat transfer path to enter the heating well 85 from the sides of the heating well 85. The heat travels from the plurality of heat transfer pins 77 through the plurality of ribs 87 which engage the heating well 85 on the underside of the top plate 83. In an embodiment, the heating well 85 has four ribs 87. More or less ribs, or ribs with other shapes and orientations may be used to transfer the heat to the heating well in alternative embodiments, given fabrication and cost considerations. The presently disclosed embodiments provide a significant increase in the heat transfer area from the heating means to the heating well.

The geometry of the plurality of ribs 87 contained in the top plate 83 and the plurality of heat transfer pins 77 in the bottom plate 75 may be optimized to promote both single well temperature uniformity and also complete heat block temperature uniformity. The optimization is obtained by the size and orientation of the rib draft angle, rib thickness versus heating well position, pin size, pin draft angle, and other design dimensions and characteristics.

The amount of pin 77 to rib 87 contact area versus well position forms a design configuration for excellent temperature uniformity across the heat block. In an embodiment, for internal wells, four pins 77 contact each heating well rib 87 and the four pins 77 share contact with two heating well ribs 87 each. In an embodiment, for edge wells, four pins 77 contact each heating well rib 87, but only three pins 77 share contact with two heating well ribs 87 each. The fourth pin 77 does not share contact with another well and therefore more heat from the fourth pin 77 is available for the edge heating wells 85 to help counteract the inherently cooler edge temperature of a heated rectangular body. The corner heating wells 85 benefit from four pins 77 which contact each heating well rib 87. Only two of the pins 77 share contact with another heating well. The other two pins 77 do not share contact with another well and even more heat is available for the corner wells to counteract the inherently cooler corner temperature of a heated rectangular body. Those skilled in the art will recognize the number of pins and ribs may vary and still be within the spirit and scope of the presently disclosed embodiments.

As shown in FIG. 1, the bottom plate 75 comprises a plurality of recesses 78. The plurality of recesses 78 have varying depths and are symmetrical about the bottom plate. 10 Each recess 78 is designed to promote the temperature uniformity across the heat block when engaged with the top plate 83. The plurality of recesses 78 form an efficient way to promote temperature uniformity since they are efficiently formed via machining, casting, or other fabrication methods known in the art. Other shapes and patterns of recesses, or no recesses, may be used in alternative embodiments. FIG. 2 shows a perspective view of the bottom plate 75 of the heat block 67. FIG. 3 shows a top perspective view of a top plate of a heat block 67. FIG. 4 shows a bottom perspective view of the top plate 83 of the heat block 67.

As shown in FIG. 5, the top plate 83 engages the bottom plate 75 to form the heat block 67. The top plate 83 may be connected to the bottom plate 75 by any mechanical engagement known in the art including, but not limited to glue, welding, snap fit, shrink fit, press fit, epoxy, adhesives and other mechanical fasteners known in the art and be within the spirit and scope of the presently disclosed embodiments. An alternative configuration could utilize a process where the bottom plate is used as a mold insert. In this way, the top plate could be molded and attached to the bottom plate during the molding process.

In addition to the top plate of the heat block having ninety-six heating wells shown in FIGS. 1-5, the heat block may have one or more dedicated wells 97 for measuring a simulated biological fluid sample temperature. The heat block may have one, two, three, four or more dedicated wells 97 for measuring a simulated biological fluid sample temperature. In an embodiment, the dedicated wells 97 for measuring a simulated biological fluid sample temperature are located along the edges of the heat block 67. Those skilled in the art will recognize that the dedicated wells 97 for measuring a simulated biological fluid sample temperature could be located along the edges, in the middle or at other locations in the top plate 83 of the heat block 67. A control system where a simulated biological fluid temperature measurement is used to make accurate transitions between biological sample fluid temperatures may also be used.

Although FIGS. 1-5 show the heat block 67 with a 96 well configuration, those skilled in the art will recognize that 48 well, 384 well, 1536 well, and other multiple well heat blocks are within the spirit and scope of the presently disclosed embodiments.

FIG. 6 shows an alternative embodiment of the heat block 67 for use with 384 well plates. The top plate 83, which can be made of a non-metal material may be molded in a variety of forms to best match commercially available sample container sizes and configurations. The 384 well format is often used for higher throughput of DNA samples. The bottom plate 75 may be cast or otherwise formed to support a variety of configurations.

FIG. 7 shows a view of a block heater 107 for heating the heat block 67. The heater 107 is positioned below the bottom plate 75 of the heat block 67. Heat is generated by the heater 107 and transferred to the bottom plate 75. The heat transfer pins 77 of the bottom plate 75 then transfer the heat to the heating wells 85 in the top plate 83 that hold the sample tubes containing samples. Placing the heater 107 below the bottom plate 75 provides an efficient and uniform transfer of heat to the samples. The heater 107 may heat the samples by resistance heating, peltier heating and cooling passive air or water heating and other heating and cooling methods known in the art and be within the spirit and scope of the presently disclosed embodiments.

The heat block 67 may be used in a variety of ways. The heat block 67 may be used in isolation to process a plurality of samples. Alternatively, the heat block 67 may be used with a plurality of additional heat blocks 67 in order to perform various processes (i.e., a first heat block delivers heat to the samples for a first time period, a second heat block delivers heat to the samples for a second time period, a third heat block delivers heat to the samples for a third time period, etc.).

The following discussion illustrates one use of the heat block 67. The following discussion is in no way meant to limit the use of the heat block of the presently disclosed embodiments. Those skilled in the art will recognize that various uses of the heat block are within the spirit and scope of the presently disclosed embodiments.

A plurality of heat blocks 67 may be used in conjunction to process a plurality of samples. The plurality of heat blocks may be utilized in a single process wherein each heat block may be operated at a different temperature. The plurality of heat blocks may be engaged to a central tube thereby creating a rotating heat assembly. The rotating heat assembly may be engaged to a processing apparatus. The rotating heat assembly may be rotated so that any of the heat blocks engaged to the rotating heat assembly may be positioned parallel to a plurality of sample tubes containing samples. The rotating heat assembly may be moved up and down in order to bring either heat block into thermal contact with the plurality of sample tubes. The presently disclosed embodiments include a method of improving PCR efficiency by using the apparatus of the presently disclosed embodiments to rapidly bring a plurality of heat blocks into and out of thermal contact with the plurality of sample tubes and avoiding the problems of raising and lowering the temperature of a single heat source.

FIG. 8 shows a perspective view of an embodiment wherein multiple heat blocks may engage a central tube 103. The central tube 103 comprises a cylindrical geometry. A first heat block, a second heat block, and a third heat block may engage the central tube 103. Those skilled in the art will recognize that the central tube 103 may have any of a variety of shapes and geometries and be within the spirit and scope of the presently disclosed embodiments.

FIG. 9 shows a perspective view of a rotating heat assembly 65 in which the plurality of heat blocks engage the central tube 103. In FIG. 9, a first heat block 67, a second heat block 69, and a third heat block 71 engage the central tube 103 to produce the rotating heat block assembly 65. The rotating heat block assembly 65 may comprise two, three, four or more heat blocks and be within the spirit and scope of the presently disclosed embodiments. Those skilled in the art will recognize that that various methods of engaging the heat blocks 67, 69, 71 to central tube 103 may be within the spirit and scope of the presently disclosed embodiments.

The rotating heat block assembly 65 may engage to a processing apparatus 100. The use of the rotating heat block assembly 65, comprising the plurality of heat blocks 67, 69, 71, allows for a plurality of samples to be processed rapidly and efficiently. Those skilled in the art will recognize that various types of processing assemblies are within the spirit and scope of the presently disclosed embodiments.

Reference will now be made to the embodiment illustrated in FIGS. 10-14, unless otherwise noted. FIGS. 10-14 illustrate an alternate embodiment of a first plate 200, a second heat block plate, which is a heating plate 300 and a complete heat block assembly 400, in accordance with the invention. The first plate 200 can be configured to be made of a thermally conductive material, can include a major upper surface having a substantially planar area and a plurality of well cavities or “heating wells” 285 for accepting a plurality of sample tubes defined therein. The term major upper surface is intended to mean an upper surface which constitutes a portion of an upper surface of the first plate 200. For example, since wells 285 are formed in the first plate 200, and interrupt the otherwise substantially planar upper surface, the space between the wells 285 is referred to as a major upper surface 283. The purpose of the first plate is consistent with that of the top plate, such as top plate 83 of FIG. 1, described above. However, as is apparent, the configuration thereof is somewhat different.

The first plate 200, in accordance with this embodiment is preferably made of a heat-conducting material such as a metal. However, metal-coated materials can be utilized, including, but not limited to metal-coated polymers, or metal-plated metals. Metals such as copper, nickel, chromium, gold, other suitable materials and combinations thereof can be used. In certain embodiments, the first plate 200 comprises a metal coating over a metal material. The metal coating is on an outer surface of the first plate 200. The metal coating acts as a wear surface and permits easy cleaning of the first plate 200. The metal coating also promotes the sensitivity of the instrument, when used to obtain quantitative data, by providing a more optically reflective surface as compared to the first plate surface (which may also be optically reflective). The metal coating or plating may comprise copper, nickel, chromium, gold, or a combination of multiple metals or other metals known to those skilled in the art. The metal coating may be applied using coating methods known in the art including, but not limited to, bath plating, physical, chemical, or ion vapor deposition, or other coating methods known in the art.

While shown in the accompanying figures as having 96 heating wells 285, first plate 200 may include 48 well, 384 well, 1536 well, and other multiple well configurations. In addition, while shown as being substantially circular in cross section, the heating wells 285 may be of any shape suitable to the use of first plate 200 in thermal cycling.

The second plate 300 is configured to serve as a heating plate, and is configured to abut the major upper surface 283 of the first plate 200, and/or to engage the first plate. The second plat preferably includes a plurality of apertures 310, defined therein, which correspond to respective wells 285 of the first plate 200. The second plate can further include a heating element 320, carried by the plate 300. Optionally, insulative portions 330 are provided between the heating element 320 and the edge of each aperture 310. The purpose of such insulation is twofold. Firstly, the insulation serves to distribute the heat from the heating element 320, allowing the edge of the aperture 310, and anything in contact therewith to change temperature more gradually than the heating element 320 itself. Further, since the insulation is slower to transfer heat, the insulation moderates any temperature fluctuations of the heating element 320, or the second plate 300 in general. When the heating element 320 is a resistive electrical heating element, the insulation also helps electrically insulate the edge of the apertures 310, through which test tubes will normally pass, from the electrical current running through the heating element 320.

This embodiment of first and second plates 200, 300, and the combined heat block assembly 400 differ from the foregoing embodiments, and typical heat blocks, in that the second plate 300, which is the heating plate, is in contact with an upper surface of the first plate. This provides certain advantages over typical heat blocks. Specifically, since the well walls 295 of heating wells 285 taper toward the bottom end 297 of each well, the cross-section of each well 285 is greater near the top of the well 285, which is in direct thermal communication with the major upper surface 283 of the first plate 200. Therefore, the upper portion of the well walls can conduct more heat than the bottom portion of the well walls. As configured in this embodiment, since heat will be applied via the second plate, which is in contact with the major upper surface 283 of the first plate 200, heat will more effectively flow to the far end of the heating well 285, which is the bottom end 297 thereof, than if heat were to flow in the opposite direction, that is, from the bottom 297 of the heating well to the top thereof, near the major upper surface 283. As embodied, improved intra-well thermal uniformity is achieved.

A further advantage of this embodiment over certain typical heating blocks, is that a negative draft angle in forming for the first plate is not needed. Some typical thermal plates, which serve a similar purpose to that of the present first plate 200, include a heating well bottom wall that is wider than the top, in order to better contact a heating element arranged on the bottom surface thereof. The present invention obviates such negative draft angle, and the cumbersome manufacturing processes needed to manufacture such components.

Still a further advantage of the embodiment of FIGS. 10-14 is that in use, convective heat losses are reduced. Since many typical heating blocks provide a heating element arranged on a bottom of the heating block, heat can be lost through convection with the surrounding environment. The second plate 300 of the present heat block 400, in use, will be situated between the first tray 200, which is intentionally heated, and a cover of a processing apparatus, such as processing apparatus 100 in FIG. 16. Accordingly, little or no portion of the second plate 300 is exposed to the surrounding environment or subject to substantial convective heat loss. As a result, the temperature uniformity among wells 285 in the first plate 200 and the heating block 400 as a whole, is improved, as compared with a heating block having an exposed heating element.

Two boss extensions 287, which extend away from the major upper surface 283, along the long edge 282 of the heat block, are used for heat block retention in a supporting frame. These bosses 287 interface with cutouts 455 in a heat block retainer 450 (FIG. 14), to capture and partially locate the heat block 400 in a heat block assembly 500. Along one or both short edges 284 of the first plate, one or more bosses 289, which can include a cavity 288 define therein, can be used to interface with a temperature sensor for simulating the temperature response of a biological sample mixture in contact with the heating wells 285, albeit if through a vial or test tube wall. While the embodiment of FIGS. 10-14 includes two such bosses 289 and cavities 288, fewer than or more than two may be provided. Moreover, the precise location of these cavities can be altered given other system design considerations, and such temperature sensors can alternatively be provided in one or more of the wells 285 of the first tray 200, as described above in connection with FIGS. 1-5.

FIG. 11 illustrates an underside of the first tray 200, in accordance with this embodiment of the invention. As can be seen, substantially cylindrical recesses 293 are provided in the bottom surface 291 of the first plate 200, opposite of the major upper surface 283. These recesses 293 promote heat block temperature uniformity in the horizontal plane by distributing the heat block mass in the horizontal plane. Such distribution can be modified by selecting appropriate diameter, location, depth or other aspects, or other attributes to the recess 293, including use of other shapes, such as polygonal shapes such as square, hexagonal and the like, or a hyperbolic shape, such as region 321 of the heating element of the second plate 300, as will be described hereinbelow.

The second plate 300, which acts as a heating plate for the subject heating block 400, is best illustrated in FIG. 12. This heater contains apertures 310 defined therein, which correspond to the heating wells 285 provided in the first plate 200. As such, in use, a sample tube, such as a vial or test tube can pass through one of the apertures 310, and into a well 285. Insulation 330 is provided around the apertures 310, and a heating element 320 passes between rows of apertures 310 and insulation 330 in a substantially serpentine manner. As can be seen, the heating element 320 begins at each end at a connecting portion 340 a, 340 b. from there, the heating element follows a path that passes between each row of apertures 310, until reaching the opposite end. This configuration helps promote temperature uniformity throughout the second plate 300, and the heating block 400 as a whole.

Insulating materials that can be used in conjunction with this second plate 300 include, but are not limited to silicone rubber, polyimide (PI), mica, polyester, nomex, and other similar materials. Such materials are described in U.S. Pat. No. 6,878,905, which is hereby incorporated by reference in its entirety. The insulating materials can be electrically insulative, thermally insulative or both electrically and thermally insulative.

The heating element 320 can include an electric resistive heating material, or can be another suitable type of heating element. A warm side of a Peltier junction can be configured to be in contact with the major upper surface 283 of the first tray 200. Alternatively, a fluid-carrying conduit can be provided, to interface with an external source for heated or cooled fluid, such as a heat pump or a hot water supply.

The heating element 320, as illustrated, includes expanded-width regions at points located between four apertures 310, such regions having a substantially hyperbola-shaped border. Accordingly, heat is provided more evenly to regions near the circumference of the apertures 310 and heating wells 285. Connection portions 340 a, 340 b are provided to enable electrical connection of the heating element 320 of the second plate 300 to an electrical source.

If desired, the heating element can be substituted for an element that can provide heat or remove heat, or alternatively still, only remove heat, depending on the desired capability of the heating block. For example, a cool side of a Peltier junction can be used in place of a resistive heating element 320. Alternatively still, if a tubular element is provided to conduct conditioning fluid, that is, heating or cooling fluid, then a cold fluid, such as chilled liquid or refrigerant can be used. If a heat pump system is utilized, then a user need only select the desired temperature, and the system will heat or cool the heating block as necessary.

The heating element 320 and/or cooling element, if so embodied, can be applied to a surface of the second plate 300, or can be embedded therein. For example, fluid-carrying tubes can be provided on or in the second plate 300. The heating/cooling elements 320 and insulation 330 can both be carried by a substrate, or can be mutually joined without a substrate, such that the second plate 300 is consistent in composition throughout cross-sections taken parallel to the substantially planar top and bottom surfaces thereof.

The first plate 200 and the second plate 300 can be joined in any suitable manner, such as those set forth above. That is, the first plate 200 can be connected to the second plate 300 by any mechanical engagement known in the art including, but not limited to glue, welding, snap fit, shrink fit, press fit, epoxy, adhesives and other mechanical fasteners known in the art and be within the spirit and scope of the presently disclosed embodiments. An alternative configuration could utilize a process where the plates are integrally formed, for example, in casting or molding.

FIG. 14 illustrates a perspective view of a rotating heat block assembly 500, in which the plurality of heat blocks 400 engage a central tube 103, similarly to the embodiment of FIG. 9. The rotating heat block assembly 500 can include two, three, four or more heat blocks and be within the spirit and scope of the presently disclosed embodiments. Those skilled in the art will recognize that that various methods of engaging the heat blocks 410 a, 410 b, 410 c to central tube 103 may be within the spirit and scope of the presently disclosed embodiments.

The rotating heat block assembly 500 can engage to a processing apparatus 100 (See FIG. 15, for example). The use of the rotating heat block assembly 500 comprising the plurality of heat blocks 410 a-410 c allows for a plurality of samples to be processed rapidly and efficiently. Those skilled in the art will recognize that various types of processing assemblies are within the spirit and scope of the presently disclosed embodiments. FIG. 15, FIG. 16 and FIG. 17 show various views of an embodiment of the processing apparatus 100. FIG. 15 shows a perspective view of the rotating heat assembly 65 as part of the processing apparatus 100. In FIG. 15, a tube cover 13 is in an open position. The tube cover 13 comprises a tube cover handle 11 for moving the tube cover 13 from an open position to a closed position. The tube cover 13 may include a tube cover heater 15. A sample retainer 43 contains a plurality of sample wells 38 for receiving a plurality of sample tubes 39. The plurality of sample tubes 39 are placed in the plurality of sample wells 38. The sample wells 38 provide a means to accommodate a variety of sample tube 39 formats commonly used for biological experiments. Some of these sample tube 39 formats include, but are not limited to, strips of eight tubes, flange connected plates of 96 tubes, single tubes, and other tube configurations known in the art. A sample carrier 45 supports the sample retainer 43.

FIG. 15 shows the rotating heat assembly 65 engaged with the processing apparatus 100. The rotating heat assembly 65 comprises a plurality of heat blocks. In FIG. 15, the rotating heat assembly 65 comprises three heat blocks: a first heat block 67, a second heat block 69 and a third heat block 71.

The first heat block 67 is capable of reaching and maintaining a first temperature, the second heat block 69 is capable of reaching and maintaining a second temperature, and the third heat block 71 is capable of reaching and maintaining a third temperature. The first temperature, the second temperature and the third temperature can be the same or distinct from one another. In some embodiments, only the first temperature and the second temperature are distinct, and the third temperature is the same as the first temperature or the second temperature. Those skilled in the art will recognize that each heat block may reach and maintain any temperature and be within the spirit and scope of the presently disclosed embodiments.

As shown in FIG. 15, the plurality of heat blocks 67, 69, 71 are engaged to the central tube 103 wherein the central tube 103 runs from a first slide 37 to a second slide 53 and the central axis of the central tube 103 is substantially horizontal.

The plurality of heat blocks 67, 69, 71 each have the top plate 83 with a plurality of heating wells 85. While the figures show the heat blocks 67, 69, 71 with the top plate 83 having 96 heating wells 85, those skilled in the art will recognize that the heat block may have 48 wells, 384 wells, 1536 wells, and other numbers of wells and be within the spirit and scope of the presently disclosed embodiments. The number of heating wells 85 in the top plate 83 corresponds to the number of sample wells 38 in the sample retainer 43.

As shown in FIG. 15, the central tube 103 is rotated by a rotation motor 49 that is mechanically connected to the central tube 103. The central tube 103 is rotated so the top plate 83 of the heat block 67, 69 or 71 is below, aligned with and substantially parallel to the sample retainer 43. Each sample well 38 of the sample retainer 43 is positioned above the heating well 85 of the top plate 83 of the heat block 67, 69 or 71. As will be discussed in greater detail below, the rotating heat assembly 65 may be raised and lowered, allowing the plurality of sample tubes 39 supported in the plurality of sample wells 38 to be received by respective ones of the plurality of heating wells 85. The plurality of sample tubes 39 are thus in thermal contact with the plurality of heating wells 85 of the top plate 83.

The rotating heat assembly 65 may be raised and lowered to any desired vertical position. The rotating heat assembly 65 may be raised and/or lowered manually or automatically using a motor 25. Those skilled in the art will recognize that various mechanisms and/or motors may be utilized to raise and lower the heat block 67 of the rotating heat assembly 65 and be within the spirit and scope of the presently disclosed embodiments.

FIG. 16 shows a close up view of the rotating heat assembly 65 as part of the processing apparatus 100. FIG. 16 shows a view from below the sample retainer 43. The rotating heat assembly 65 is engaged to the processing apparatus 100. The top plate 83 of the second heat block 69 is below, aligned with and substantially parallel to the sample retainer 43. The plurality of heating wells 85 of the second heat block 69 are positioned beneath the plurality of sample tubes 39. The plurality of sample tubes 39 are located within the plurality of sample wells 38 of the sample retainer 43. A sample fluid sensor 57 or a plurality of sample fluid sensors 57 are operatively connected to the sample retainer 43.

The rotating heat assembly 65 may be rotated to a desired position. As shown in FIG. 16, a rotational position sensor 63 is in communication with the rotating heat assembly 65. The rotational position sensor 63 controls and/or indicates the current rotational position of the rotating heat assembly 65. The rotating heat assembly 65 may be raised or lowered to a desired vertical position. A vertical position sensor 59 is in communication with the top plate 83 of the heat block 67. The vertical position sensor 59 controls and/or indicates the current vertical position of the rotating heat assembly 65. The position sensors 59, 63 provide a repeatable position signal. The position sensors 59, 63 are selected to support a position resolution sufficient for reliable motion. In an embodiment, the position sensors 59, 63 comprise multiple terminals for wire harness connection. Those skilled in the art will recognize that various rotational and/or vertical position sensors known in the art may be within the spirit and scope of the presently disclosed embodiments.

FIG. 17 shows a perspective view of the rotating heat assembly 65 as part of the processing apparatus 100. In FIG. 17, the tube cover 13 has been lowered to a closed position to cover the sample retainer 43 and the plurality of sample tubes 39. The tube cover 13 comprises the tube cover heater 15 (shown in FIG. 15). Closing the tube cover 13 and activating the tube cover heater 15 heats the plurality of sample tubes 39. The tube cover heater 15 provides heat to the plurality of sample tubes 39 to provide a desired temperature profile. The tube cover heater 15 may provide a constant temperature or a variable temperature during processing of the plurality of sample tubes 39. The tube cover heater 15 may be used in conjunction with the rotating heat assembly 65 to achieve a desired temperature profile of the plurality of sample tubes 39. Those skilled in the art will recognize that various temperature profiles are within the spirit and scope of the presently disclosed embodiments.

The tube cover 13 comprises a temperature sensor to sense a cover temperature so that this temperature may be actively controlled. The temperature sensor may be a thermistor engaged to the tube cover 13. The thermistor has multiple lead wires that exit the tube cover 13 and are operatively connected to the thermal system.

A temperature sensor may be positioned in a sample container within a sample well 38 of the sample retainer 43 to measure the temperature of the heat block 67. The temperature data from the temperature sensor is sent to a controller which will then adjust the amount of heat provided by the heat source. The temperature sensor may be a thermistor. The thermistor accurately controls the components involved in a temperature transition. Those skilled in the art will recognize that thermocouples, resistance temperature detectors (RTD) or other temperature sensors known in the art are within the spirit and scope of the presently disclosed embodiments.

The presently disclosed embodiments provides a method of performing thermal cycling comprising placing at least one sample tube 39 in at least one sample well 38 of the sample retainer 43 engaged to a main frame of the processing assembly 100. The rotating heat assembly 65 is rotated so the top plate 83 of the first heat block 67 is positioned below the sample retainer 43. The top plate 83 comprises at least one heating well 85. The rotating heat assembly 65 is raised to bring the heating well 85 into thermal contact with the plurality of sample tubes 39 and allow the heating wells 85 remain in thermal contact with the plurality of sample tubes 39 for a first time period at a first temperature. The rotating heat assembly 65 is lowered to separate the plurality of heating wells 85 from the plurality of sample tubes 39 so the heating wells 85 and sample tubes 39 are no longer in thermal contact.

The second heat block 69 is heated to a second temperature and the second heat block 69 is rotated into a position below the sample retainer 43. The rotating heat assembly 65 is raised to bring the second heat block 69 into thermal contact with the plurality of sample tubes 39. The plurality of heating wells 85 remain in thermal contact with the plurality of sample tubes 39 for a second time period at a second temperature so the samples in the plurality of sample tubes 39 attain a desired temperature profile. The rotating heat assembly 65 is lowered after the second heat block 69 has heated the plurality of sample tubes 39 for a sufficient time period. The rotating heat assembly 65 is lowered to separate the plurality of heating wells 85 from the plurality of sample tubes 39 so the heating wells 85 and sample tubes 39 are no longer in thermal contact.

The third heat block 71 is heated to a third temperature and the third heat block 71 is rotated into a position below the sample retainer 43. The rotating heat assembly 65 is raised to bring the third heat block 71 into thermal contact with the plurality of sample tubes 39. The plurality of heating wells 85 remain in thermal contact with the plurality of sample tubes 39 for a third time period at a third temperature so the samples in the plurality of sample tubes 39 attain a desired temperature profile. The rotating heat assembly 65 is lowered after the third heat block 71 has heated the plurality of sample tubes 39 for a sufficient time period. The rotating heat assembly 65 is lowered to separate the plurality of heating wells 85 from the plurality of sample tubes 39 so the heating wells 85 and sample tubes 39 are no longer in thermal contact.

The method may be repeated for multiple heat blocks. The heat blocks may operate at a constant temperature or a variable temperature while in thermal communication with the plurality of sample tubes. The heat blocks of the rotating heat assembly may operate at varying temperature and for varying time periods for the samples to reach a desired temperature profile.

Other sample holding structures such as slides, partitions, beads, channels, reaction chambers, vessels, surfaces, or any other suitable device for holding a sample can be used with the presently disclosed embodiments. The samples to be placed in the sample holding structure are not limited to biological reaction mixtures. Samples could include any type of product for which it is desired to heat and/or cool, such as cells, tissues, microorganisms or non-biological product.

Each sample tube 39 can have a corresponding cap for maintaining the biological reaction mixture in the sample tube. The caps are typically inserted inside the top cylindrical surface of the sample tube. The caps are relatively clear so that light can be transmitted through the cap. Similar to the sample tubes, the caps are typically made of molded polypropylene, however, other suitable materials are acceptable. Each cap has a thin, flat, plastic optical window on the top surface of the cap. The optical window in each cap allows radiation such as excitation light to be transmitted to the DNA samples and emitted fluorescent light from the DNA to be transmitted back to an optical detection system during cycling.

Heat blocks in accordance with the invention can be used with thermal cyclers of various makes and models, and is not limited to use in a thermal cycler as exemplified in FIGS. 8, 9 and 14-17. Other thermal cycler systems and methods of detecting the fluorescence from a PCR reaction could also benefit from a heat block of the presently disclosed embodiments. For example, the heat block could be used with the apparatus for thermally cycling samples of biological material described in assignee's U.S. Pat. No. 6,657,169, and the entirety of this patent is hereby incorporated herein by reference. The heat block can also be used with the Mx3000P Real-Time PCR System and the Mx4000 Multiplex Quantitative PCR System (commercially available from Stratagene Calif. in La Jolla, Calif.) using a tungsten halogen bulb that sequentially probes each sample, detected with a photomultiplier tube. In addition, the heat block could be used with thermal cyclers incorporating any or all of the following: a tungsten halogen bulb that sequentially probes each sample; a scanning optical module; stationary light emitting diodes (LEDs) for each well and the same detector for all wells; stationary samples, light sources, and detectors; stationary LEDs and a detector to probe spinning samples sequentially; a tungsten halogen bulb to illuminate the entire plate and a charge-coupled device detection of the entire plate; a stationary light source and multiple detectors sampling spinning capillaries sequentially; a stationary laser and detector that sequentially probes stationary samples using independent fiber optics collecting light from each sample; a tungsten halogen bulb to illuminate the entire plate and charge-coupled device detection of the entire plate, and other thermal cyclers known in the art.

All patents, patent applications, and published references cited herein are hereby incorporated by reference in their entirety. It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. 

1. A heat block comprising: a top plate comprising a non-metal material wherein the top plate comprises a plurality of heating wells for accepting a plurality of sample tubes; a bottom plate engaging the top plate; and a plurality of heat transfer pins extending from the bottom plate to the top plate to transfer heat from the bottom plate to the top plate.
 2. The heat block of claim 1 further comprising a heater thermally connected to the bottom plate.
 3. The heat block of claim 1 wherein the non-metal material of the top plate is a molded plastic.
 4. The heat block of claim 1 wherein the non-metal material is coated with a metal plating.
 5. The heat block of claim 1 wherein the bottom plate comprises aluminum.
 6. The heat block of claim 1 wherein at least one heating well measures a simulated biological fluid sample temperature.
 7. A heat block comprising: a top plate comprising a non-metal core with a metal coating on an outer surface; a plurality of heating wells formed in the top plate for supporting a plurality sample tubes; a bottom plate engaged to the top plate wherein the bottom plate comprises a metal; and a plurality of heat transfer pins extending from the bottom plate to the top plate to uniformly heat the heat block.
 8. The heat block of claim 7 further comprising a heater in thermal contact with the bottom plate.
 9. The heat block of claim 7 wherein the non-metal material of the top plate is a molded plastic.
 10. The heat block of claim 7 wherein the metal coating comprises aluminum.
 11. The heat block of claim 7 wherein the metal coating comprises copper.
 12. The heat block of claim 7 wherein the top plate engages the bottom plate by an epoxy.
 13. A method of thermal cycling samples comprising: placing a plurality of sample tubes containing samples in a sample retainer, rotating a rotating heat assembly to position a top plate of a heat block below the sample retainer, the top plate comprising a plurality of heating wells; raising the rotating heat assembly to bring the plurality of heating wells of the top plate in thermal contact with the plurality of sample tubes; heating the heat block to a first temperature for a first time period to control a temperature of the samples in the plurality of sample tubes; and lowering the rotating heat assembly so the plurality of heating wells of the top plate are no longer in thermal contact with the plurality of sample tubes.
 14. The method of claim 13 further comprising: rotating the rotating heat assembly to position a top plate of a second heat block below the sample retainer, the top plate of the second heat block comprising a plurality of heating wells; raising the rotating heat assembly to bring the plurality of heating wells of the top plate in thermal contact with the plurality of sample tubes; heating the heat block to a second temperature for a second time period to control the temperature of the samples in the plurality of sample tubes; and lowering the rotating heat assembly so the plurality of heating wells of the top plate are no longer in thermal contact with the plurality of sample tubes.
 15. The method of claim 14 further comprising: rotating the rotating heat assembly to position a top plate of a third heat block below the sample retainer, the top plate of the third heat block comprising a plurality of heating wells; raising the rotating heat assembly to bring the plurality of heating wells of the top plate in thermal contact with the plurality of sample tubes; heating the heat block to a third temperature for a third time period to control the temperature of the samples in the plurality of sample tubes; and lowering the rotating heat assembly so the plurality of heating wells of the top plate are no longer in thermal contact with the plurality of sample tubes.
 16. The method of claim 15 wherein the first time period, the second time period and the third time period are each different.
 17. The method of claim 15 wherein the first temperature, the second temperature and the third temperature are each different.
 18. A method for heating a plurality of heating wells comprising; providing a heat block having a top plate comprising a non-metal material and a bottom plate with a plurality of heat transfer pins engaging a plurality of heating wells of the top plate; placing the plurality of heating wells in thermal contact with a plurality of sample tubes; heating the bottom plate of the heat block with a heater; and transferring heat from the bottom plate to the plurality of heating wells by the plurality of heat transfer pins.
 19. The method of claim 18 wherein the non-metal material of the top plate is a molded plastic.
 20. The method of claim 18 wherein the non-metal material of the top plate is coated with a metal plating.
 21. The method of claim 18 wherein the bottom plate comprises aluminum.
 22. The method of claim 18 further comprising transferring heat from the plurality of heating wells to the plurality of sample tubes.
 23. The method of claim 18 further comprising measuring a simulated biological fluid temperature to make accurate transitions between biological sample fluid temperatures.
 24. A heat block comprising: a thermal plate comprising a thermally conductive material, the thermal plate including a major upper surface having a substantially planar area and a plurality of heating wells for accepting a plurality of sample tubes; and a heating plate engaging the thermal plate and contacting the major upper surface of the thermal plate.
 25. The heat block of claim 24, wherein said thermally conductive material is aluminum.
 26. The heat block of claim 24, wherein said thermal plate includes a boss having a cavity defined therein to simulate a temperature response of a biological sample.
 27. The heat block of claim 24, wherein at least one heating well measures a simulated biological fluid sample temperature.
 28. A method for heating a plurality of heating wells comprising; providing a heat block having: a thermal plate comprising a thermally conductive material, the thermal plate including a major upper surface having a substantially planar area and a plurality of heating wells for accepting a plurality of sample tubes; and a heating plate engaging the thermal plate and contacting the major upper surface of the thermal plate; placing the plurality of heating wells in thermal contact with a plurality of sample tubes; heating the thermal plate of the heat block with the heating plate; and transferring heat from the thermal plate to the plurality of heating wells through conductive heat transfer.
 29. A heat block comprising: a first plate having a substantially planar major upper surface and a plurality of heating wells defined in the major upper surface for accepting a plurality of sample tubes; and a second plate abutting the major upper surface of the first plate, the second plate being a heating plate having: a body portion having a plurality of apertures formed therein; an insulative portion surrounding the plurality of apertures; and a heating element carried by the heating plate, arranged between insulative portions thereof.
 30. The heat block of claim 29, wherein the body portion of the second plate is substantially planar in shape.
 31. The heat block of claim 29, wherein the heating element is a resistive heating element.
 32. The heat block of claim 29, wherein the heating element is a tubular conduit for carrying heated fluid.
 33. The heat block of claim 29, wherein the heating element is secured to a bottom surface of the second plate, for contacting the first plate.
 34. The heat block of claim 29, wherein the heating element is embedded in the second plate.
 35. The heat block of claim 29, wherein the heating element is formed within in the second plate.
 36. The heat block of claim 29, wherein the insulative portion is thermally insulative.
 37. The heat block of claim 29, wherein the insulative portion is electrically insulative.
 38. The heat block of claim 29 further comprising connecting portions for connecting the heating element of the second plate to a heat energy source.
 39. The heat block of claim 36, wherein the heat energy source is an electrical energy source for providing an electrical current to the heating element.
 40. The heat block of claim 36, wherein the heat energy source is source provides heated fluid to the heating element.
 41. The heat block of claim 29, wherein the first plate comprises a metal material
 42. The heat block of claim 41, wherein the metal material is selected from the group consisting essentially of copper, aluminum, brass and combinations thereof.
 43. The heat block of claim 41, wherein the metal material comprises a first metal coated with a second metal.
 44. The method of thermal cycling of claim 13, wherein the heat block comprises: a first plate having a substantially planar major upper surface and a plurality of heating wells defined in the major upper surface for accepting a plurality of sample tubes; and a second plate abutting the major upper surface of the first plate, the second plate being a heating plate having: a body portion having a plurality of apertures formed therein; an insulative portion surrounding the plurality of apertures; and a heating element carried by the heating plate, arranged between insulative portions thereof. 